The present invention relates to an apparatus for extrusion of a flowable mass onto a moving surface, and more particularly relates to the control and recycling of excess mass which fails to properly extrude from a double cylinder extrusion apparatus.
A variety of apparatus for extruding a mass onto a moving support mechanism are known. One such apparatus is shown in U.S. Pat. No. 4,279,579 ("the '579 patent), the teachings of which are incorporated herein by reference.
The extrusion apparatus described in the '579 patent utilizes two concentric cylindrical containers. The inner container receives the mass to be extruded and has a row of apertures or a slot which faces in the direction of a moving conveyor belt. The outer container is designed to rotate about the inner container and has a plurality of apertures disposed throughout its surface. When the apertures in the surface of the outer container are aligned with the apertures or slot of the inner container, the mass to be extruded flows from the inner container, through the outer container and ultimately onto the moving conveyor. Since the outer container is rotating, it acts like a knife to separate the extruded matter from the apparatus so that it flows onto the conveyor in droplet or other forms.
An amount of excess mass typically tends to remain on the outer surface of the outer cylinder in the regions of the apertures after the mass has been extruded onto the conveyor. For this reason, the '579 patent teaches the use of a spatula to scrape the surface of the cylinder to force the excess mass back into the apertures of the outer cylinder. This method of removing the excess mass, however, is somewhat wasteful since much of the excess mass is not automatically recycled when the spatula merely functions as a scraper. Rather, the excess mass must be manually recycled once it has accumulated in, for example, a drum that receives the excess mass from the spatula. Furthermore, the excess mass may tend to clog the apertures in the outer cylinder when it is forced back by the spatula.
A further embodiment of the '579 patent is directed to creating a negative pressure in the interstitial region between the inner and outer cylinders. However, the pressure, if any, so generated must be sufficient to draw or suck the amount of excess material back into the region. Thus, where the amount of excess material is significant, the pressure may not be sufficient to draw all of the excess mass therein.
It is therefore an object of the present invention to improve the performances of a double cylinder extruding apparatus in order to automatically recycle the excess mass which fails to properly extrude onto the moving support mechanism.